Sunlight readable LCD with uniform in-cell retarder

Abstract

A display device in which ambient light reflections, for example, from IPS or FFS type displays are reduced by a circular polariser (e.g., linear polariser combined with external quarter waveplate) to make the light circular polarized, as it traverses the multiple reflective layers between the polariser and LC layer, and then an internal quarter waveplate converts the light back to linear polarisation before it enters the LC, so the display can operate as normal, while the circular polariser absorbs unwanted reflections of ambient light from within the display.

The invention claimed is: 
     
       1. An FFS or IPS type LCD comprising, from the viewing side:
 a first linear polariser with a transmission axis in a first direction; 
 an unpatterned external quarter wave plate with an optical axis arranged at 45° to the first direction; 
 a top substrate; 
 a patterned black mask layer; 
 a reactive mesogen alignment layer that promotes an alignment direction of a reactive mesogen material at 45° to the first direction; 
 an unpatterned internal quarter wave plate that is comprised of the reactive mesogen material; 
 a patterned colour filter layer 
 a first LC alignment layer 
 an LC layer that is aligned in a direction that is either parallel to, or perpendicular to, the first direction; 
 a second LC alignment layer; 
 a patterned TFT layer for one or more pixels; 
 a bottom substrate; and 
 a second linear polariser with a transmission axis in a second direction that is perpendicular to the first direction. 
 
     
     
       2. The FFS or IPS type LCD of  claim 1 , wherein the linear polariser and the unpatterned external quarter wave plate form a circular polariser, and the internal quarter wave plate or external quarter waveplate are either of the same birefringence polarity and oriented with their optics axes at 90° to each other, or are of opposite birefringence polarity and have their optic axes oriented parallel. 
     
     
       3. The FFS or IPS type LCD of  claim 2 , in which the LCD is a transflective type LCD, the LCD including a pixel area having a reflective portion comprising a reflective element disposed between the bottom substrate and LC layer. 
     
     
       4. The FFS or IPS type LCD of  claim 2 , wherein the LCD is a transflective type LCD, the LCD including a second external quarter wave plate positioned between the second linear polariser and the bottom substrate. 
     
     
       5. The FFS or IPS type LCD of  claim 2 , wherein the LCD is a transflective type LCD, the LCD including a second internal quarter waveplate positioned between the TFT layer and the LC layer. 
     
     
       6. The FFS or IPS type LCD of  claim 3 , further comprising a pixel electrode formed of electrode fingers to apply an electric field to the LC crystal layer and in which an electrode finger angle of the pixel electrode is different in transmissive and reflective portions of the pixel. 
     
     
       7. The FFS or IPS type LCD of  claim 2 , further comprising an additional at least partially reflective layer included between the circular polariser and the internal quarter wave plate. 
     
     
       8. The FFS or IPS type LCD of  claim 2 , in which electrodes of a touch panel are included between the circular polariser and the internal quarter wave plate. 
     
     
       9. The FFS or IPS type LCD of  claim 1 , in which the LCD is a transflective type LCD having first and second parts of a pixel area, the first part including a reflector in the light path to reflect light transmitted through the LC layer back through the LC layer, and the second part including a light path from a light input at one end of the LCD to a light output at an opposite end of the LCD. 
     
     
       10. The FFS or IPS type LCD of  claim 1 , wherein the external quarter waveplate is a laminated film that includes a cyclo-olefin polymer (COP) material. 
     
     
       11. The FFS or IPS type LCD of  claim 1 , wherein an overcoat layer is deposited on the non-viewing side of the patterned colour filter layer. 
     
     
       12. An LCD structure including the FFS or IPS type LCD of  claim 1  and a display area comprising one or more pixels, wherein the FFS or IPS type LCD is configured to reduce unwanted reflections from at least part of the display area of the LCD structure. 
     
     
       13. An FFS or IPS type LCD comprising, from the viewing side:
 a first linear polariser with a transmission axis in a first direction; 
 an unpatterned external quarter wave plate with an optical axis arranged at 45° to the first direction; 
 a top substrate; 
 a patterned TFT layer for one or more pixels; 
 a layer comprising in combination a patterned black mask and patterned colour filters; 
 a reactive mesogen alignment layer that promotes an alignment direction of a reactive mesogen material at 45° to the first direction; 
 an unpatterned internal quarter wave plate that is comprised of the reactive mesogen material; 
 a first LC alignment layer; 
 an LC layer that is aligned in a direction that is either parallel to, or perpendicular to, the first direction; 
 a second LC alignment layer; 
 a bottom substrate; and 
 a second linear polariser with a transmission axis in a second direction that is perpendicular to the first direction. 
 
     
     
       14. The FFS or IPS type LCD of  claim 13 , wherein the linear polariser and the unpatterned external quarter wave plate form a circular polariser, and the internal quarter wave plate or external quarter waveplate are either of the same birefringence polarity and oriented with their optics axes at 90° to each other, or are of opposite birefringence polarity and have their optic axes oriented parallel. 
     
     
       15. The FFS or IPS type LCD of  claim 13 , wherein an overcoat layer is deposited on the non-viewing side of the layer comprising in combination the patterned black mask and patterned colour filters. 
     
     
       16. An LCD structure including the FFS or IPS type LCD of  claim 13  and a display area comprising one or more pixels, wherein the FFS or IPS type LCD is configured to reduce unwanted reflections from at least part of the display area of the LCD structure. 
     
     
       17. An FFS or IPS type LCD comprising, from the viewing side:
 a first linear polariser with a transmission axis in a first direction; 
 an unpatterned external quarter wave plate with optical axis arranged at 45° to the first direction; 
 a top substrate; 
 a patterned TFT layer for one or more pixels; 
 a reactive mesogen alignment layer that promotes an alignment direction of a reactive mesogen material at 45° to the first direction; 
 an unpatterned internal quarter wave plate that is comprised of the reactive mesogen material; 
 a layer comprising in combination a patterned black mask and patterned colour filters; 
 a first LC alignment layer 
 an LC layer that is aligned in a direction that is either parallel to, or perpendicular to, the first direction; 
 a second LC alignment layer; 
 a bottom substrate; and 
 a second linear polariser with a transmission axis in a second direction that is perpendicular to the first direction. 
 
     
     
       18. The FFS or IPS type LCD of  claim 17 , wherein the linear polariser and the unpatterned external quarter wave plate form a circular polariser, and the internal quarter wave plate or external quarter waveplate are either of the same birefringence polarity and oriented with their optics axes at 90° to each other, or are of opposite birefringence polarity and have their optic axes oriented parallel. 
     
     
       19. The FFS or IPS type LCD of  claim 17 , wherein an overcoat layer is deposited on the non-viewing side of the layer comprising in combination a patterned black mask and patterned colour filters. 
     
     
       20. An LCD structure including the FFS or IPS type LCD of  claim 17  and a display area comprising one or more pixels, wherein the FFS or IPS type LCD is configured to reduce unwanted reflections from at least part of the display area of the LCD structure.